The foremost research objectives of this project involve the conception and formulation of new materials, or modifications of already existing materials, in order to improve the quality of crown and bridge prostheses both in porcelain-metal restorations as well as those made of complete cast pieces. In a broad concept this proposal involves: (1) studying the tarnish resistant properties of a Au-Pd-Ag-Cu alloy system in vivo and correlating them to in vitro tests; (2) studying the castability, fit, and solderability of cast restorations of the above system; (3) studying the nature of the metal-porcelain interface, identification of compounds, and strength of the metal-porcelain interface; (4) esthetic quality of porcelain restorations of the Au-Pd-Ag-Sn-In system as well as that of the Pd-Ag-Sn-In and base metal alloy system; (5) possible modification of centrifugal casting machines in order to obtain a better and more complete cast piece when lower density alloys, such as alloys of Pd-Ag systems and base metals, are used; and (6) modification or alteration of the composition of dental investments to produce the necessary and required expansion of the mold cavity to compensate for the shrinkage of cast base metal alloys.